Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.11 (AMPK)
 12,425 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) which catalyzes the phosphorylation of troponin T, phosvitin and casein has been purified over 2000 fold from rabbit skeletal muscle. The partial purification of this new enzyme, designated troponin T kinase, involves precipitation of contaminating proteins at pH 6.1, fractionation of the supernatant with (NH4)2SO4 and successive column chromatographies on DEAE-cellulose, hydroxyapatite and Sepharose 6B. The chromatographic patterns on DEAE-cellulose and hydroxyapatite columns show two peaks of troponin T kinase activity. Gel filtration experiments indicate the existence of multiple, possibly aggregated, forms of the enzyme. The purified enzyme does not catalyze the phosphorylation of phosphorylase b, troponin I, troponin C, tropomyosin, protamine, or myosin light chain 2 nor does it catalyze the interconversion of glycogen synthase I into the D form. Troponin T kinase is not affected by the addition of cyclic nucleotides or AMP to the reaction mixture. Divalent cations (other than Mg2+, required for the reaction) do not stimulate the enzyme, and several are inhibitory. Other characteristics of the reaction catalyzed by troponin T kinase, such as Km values for ATP and substrate proteins, pH optima, effect of the concentration of Mg2+, substitution of ATP for GTP have also been studied.
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PMID:Purification and properties of troponin T kinase from rabbit skeletal muscle. 3 14

The effects of histamine on heart cAMP-dependent protein kinase activity, cAMP levels, phosphorylase activity, and contractile force was investigated in the perfused guinea pig heart. To accurately determine the protein kinase activity ratio in guinea pig heart, it was necessary to measure kinase activity in whole homogenates immediately after homogenization of the tissue. Histamine produced a rapid dose-dependent increase in cAMP and the protein kinase activity ratio followed by increased in contractile force and phosphorylase activity. There was a good correlation between the degree of protein kinase activation and the increase in phosphorylase and force. The beta-adrenergic blocking agent propranolol did not reduce the effects of histamine, but metiamide, a potent H2-receptor antagonist, greatly attenuated all the effects of histamine. The data support the hypothesis that increases in heart cAMP-dependent protein kinase activity produce corresponding increases in contractile force and phosphorylase activity.
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PMID:Involvement of cAMP-dependent protein kinase in the regulation of heart contractile force. II. 8 6

Liver glycogen synthase b phosphatase, chromatographically separable from phosphorylase a phosphatase, is decreased in 48-hour alloxan diabetic rats. The phosphatase activities are measured in an in vitro system using exogenous isolated phospho-enzyme as substrates with added phosphatases. Synthase and phosphorylase phosphatases were shown to have differential catalytic properties by their reactivity in the presence of Pi, the heat-stable inhibitor of phosphorylase phosphatase and after incubation with added cAMP-dependent protein kinase.
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PMID:Insulin sensitivity of liver glycogen synthase b into a conversion. 11 80

Partially purified rabbit skeletal muscle phosphorylase phosphatase (EC 3.1.3.17; phosphoprotein phosphohydrolase) was inactivated when it was incubated with exogenous cyclic AMP-dependent protein kinase (EC 2.7.1.37; ATP:protein phosphotransferase), cyclic AMP, and ATP-Mg. Subsequent separation of the phosphatase by acrylamide gel electrophoresis or sucrose density centrifugation resulted in reactivation of the enzyme. The phosphatase decreased in molecular weight from approximately 70,000 to 52,000, and a phosphorylated inhibitor with molecular weight of 26,000 was found. Reactivation of phosphatase also occurred when it was incubated with MnCl2 or trypsin. The inhibitor was effective at less than 10(-8) M and was relatively heat stable. Its activity was destroyed by tryptic digestion and by dephosphorylation by a Mn-stimulated phosphatase. These observations support the possibility that phosphorylase phosphatase activity is controlled by cyclic AMP-dependent protein kinase and a Mn-stimulated phosphatase by a reaction involving phosphorylation and dephosphorylation of a protein phosphatase inhibitor.
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PMID:Inactivation of rabbit muscle phosphorylase phosphatase by cyclic AMP-dependent kinas. 17 49

Glucagon causes a rapid activation of cAMP-dependent protein kinase in rat liver parenchymal cells which correlates well with the accumulation of cAMP. Full activation of phosphorylase or inactivation of glycogen synthase is achieved with half-maximal or less activation of protein kinase. Epinephrine stimulates glycogen breakdown in these cells mainly by mechanisms involving alpha-adrenergic receptors and not beta-receptors. Activition of alpha-receptors results in rapid activation of phosphorylase and inactivation of glycogen synthase without accumulation of cAMP or activation of cAMP-dependent protein kinase. Activation of beta-receptors causes a transient rise in cAMP and a short-lived activation of protein kinase with correspondingly little stimulation of glycogenolysis.
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PMID:Studies on the role of cAMP-dependent protein kinase in the actions of glucagon and catecholamines on liver glycogen metabolism. 18 93

There is broad species variation in the type of cAMP-dependent protein kinase isozyme present in supernatant fractions of heart homogenates as determined by DEAE-cellulose chromatography, Isozyme I, which elutes at less than 0.1 M NaCl, is predominant in mouse and rat hearts; while isozyme II, which elutes at greater than 0.1 M NaCl, is the predominant type in beef and guinea pig. Human and rabbit hearts contain about equal amounts of the two types. The type I heart kinases are more easily dissociated into free regulatory and catalytic subunits by incubation with histone than are the type II kinases, and the separated regulatory and catalytic subunits of isozyme II of rat heart reassociate more rapidly than the subunits of isozyme I under the conditions used. The data from several experiments using rat heart indicate that the basal activity ratio of the protein kinase in crude extracts (approximately 0.15) is due mainly to basal endogenous cAMP and that cAMP elevation accounts entirely for the epinephrine effect on the enzyme. Addition of epinephrine and 1-methyl-3-isobutylxanthine to the perfusate causes a rapid (1 min) increase in cAMP, active supernatant protein kinase, and active phosphorylase in perfused hearts of both rat (mainly isozyme I) and guinea pig (mainly isozyme II). The elevation percentage in cAMP is about the same in the two species, but the increase in active protein kinase is greater in rat heart. If hearts from either animal are perfused continually (10 min) with epinephrine (0.8 muM) and 1-methyl-3-isobutylxanthine (10 muM), the cAMP level, active protein kinase, and active phosphorylase remain elevated. Likewise, all parameters return rapidly to the basal levels when epinephrine and 1-methyl-3-isobutylxanthin are removed. Most of the epinephrine effect on the rat heart supernatant kinase is retained at 0 degrees if cAMP is removed by Sephadex G-25 chromatography, although this procedure completely reverses the epinephrine effect in the guinea pig heart. The epinephrine effect on the rabbit heart kinase (approximately equal amounts of isozymes I and II) is partially reversed by Sephadex G-25. These species differences can be accounted for by differences in association-dissociation behavior of the isozymes in vitro. The data suggest that epinephrine causes activation of both isozymes. The activity present in the particulate fraction comprises nearly half of the total cAMP-dependent protein kinase activity in homogenates of rabbit heart. Triton X-100 extracts of low speed particulate fractions from hearts of each species tested, including rat heart, contain predominantly or entirely the type II isozyme, suggesting differences in intracellular distribution of the isozymes. The binding of the protein kinase to the particulate fraction is apparently due to the properties of the regulatory subunit component. Differences in topographical distribution of the isozymes could provide for differences in either physiological regulation or substrate specificity.
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PMID:Characterization and regulation of heart adenosine 3':5'-monophosphate-dependent protein kinase isozymes. 19 Feb 20

The effects of perfusate epinephrine, 1-methyl-3-isobutylxanthine, calcium, and filling pressure were investigated in the perfused working rat heart. Epinephrine produced a rapid increase in cAMP, in the protein kinase activity ratio, and in active phosphorylase. These effects preceded the increase in contractile force produced by the hormone. There was good correlation between protein kinase activation and the increase in force. Epinephrine and the phosphodiesterase inhibitor 1-methyl-3-isobutylxanthine were synergistic in their stimulatory effects on cAMP, protein kinase activity, active phosphorylase, and contractile force. When an increase in the force of contraction was produced either by increasing the filling pressure of the heart or by increasing the perfusate Ca2+ concentration, there was no change in either cAMP levels or protein kinase activity. These data suggest that the effect of beta-adrenergic catecholamines on contractile force is due, at least in part, to cAMP-dependent protein kinase activation. The increase in contractile force produced either by increasing the filling pressure (Frank-Starling phenomenon) or by increasing the perfusate Ca2+ concentration is apparently not mediated by cAMP or the protein kinase.
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PMID:Involvement of cAMP-dependent protein kinase in the regulation of heart contractile force. 19 11

The effect of prostaglandin E1(PGE1) and epinephrine on glycogen metabolism has been investigated in the perfused rat heart. Both agents produced increases in cAMP and the cAMP-dependent protein kinase activity ratio. When dosages were adjusted to give equal increases in the protein kinase activity ratio from a basal value of 0.15 to as high as 0.40, only epinephrine caused a significant increase in phosphorylase activity. When used together, PGE1 did not effect the ability of epinephrine to increase phosphorylase activity.
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PMID:Activation of cAMP-dependent protein kinase without a corresponding increase in phosphorylase activity. 19 22

In the isolated perfused rat heart, epinephrine produced a rapid, concentration-dependent increase in cyclic adenosine 3',5'-monophosphate (cAMP), activation of cAMP-dependent protein kinase, activation of phosphorylase, and increase in contractile force. At epinephrine concentrations of 1 micron or less, acetylcholine antagonized all these beta-adrenergic effects and also increased cyclic guanosine 3',5'-monophosphate (cGMP) levels. When used alone, acetylcholine produced a rapid elevation of cGMP and markedly diminished contractile force but did not significantly lower basal cAMP levels or cAMP-dependent protein kinase activity. The data suggest that changes in cAMP-dependent protein kinase activity can explain the antagonism of epinephrine-induced activation of phosphorylase by acetylcholine, but cannot completely account for the inhibitory effect of the cholinergic agent on contractile force.
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PMID:Interaction of acetylcholine and epinephrine on heart cyclic AMP-dependent protein kinase. 20 51

The relationship between cAMP-dependent protein kinase activity and epinephrine-produced activation of phosphorylase and increase in contractility was investigated in the intact working rat heart. Epinephrine was administered as a bolus into the superior vena cava of open-chest preparations and the hearts were rapidly frozen. cAMP increased within 5 s and returned to control within 20-30 s. Protein kinase and phosphorylase kinase activity ratios increased transiently with the same time course as that for cAMP. The phosphorylase activity ratio and the rate of left ventricular pressure development increased maximally within 15 s and returned to control in 30-60 s. Continuous infusion of epinephrine caused a sustained elevation of the protein kinase. Free catalytic protein kinase activity increased proportionately with the dose of epinephrine. The beta-adrenergic blocking agent, practolol, had no effect on the basal levels of the five parameters studied, but did prevent the epinephrine-produced increases. The results suggest that the time course of cAMP-dependent protein kinase activation is appropriate if this enzyme is to play a role in the catecholamine-induced increase in both glycogenolysis and contractility in the in vivo heart.
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PMID:Protein kinase regulation of cardiac phosphorylase activity and contractility. 20 58


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